Various kinds of treatment apparatuses are known that comprise a treatment unit to be supplied with a fluid. The known treatment apparatuses include, for example, blood treatment apparatuses. During the blood treatment, the patient's blood flows in an extracorporeal blood circuit through the blood treatment unit. In the case of apparatuses for hemodialysis, hemofiltration and hemodiafiltration, the blood treatment unit is a dialyzer or filter, which is divided by a semi-permeable membrane into a blood chamber and a dialyzing fluid chamber. During the dialysis treatment, the blood flows in an extracorporeal blood circuit through the blood chamber, whilst the dialyzing fluid flows in a dialyzing fluid circuit through the dialyzing fluid chamber of the dialyzer.
On account of the large exchange quantities, there is a need with the known methods and apparatuses for blood treatment for an exact balancing of the fluid removed from the patient and the fluid fed to the patient during the overall treatment time. Gravimetric and volumetric balancing devices belong to the prior art.
A hemodiafiltration apparatus with volumetric balancing is known for example from DE 26 34 238 A1. The balancing device of the known hemodiafiltration apparatus comprises a volume-rigid hollow body, which is divided by a mobile partition wall into two chambers. Each chamber comprises an inlet and an outlet, on which supply lines and discharge lines for fresh and, respectively, used dialyzing fluid are disposed, a shut-off element being incorporated in each line. Moreover, provision is made for pumps for conveying the fresh and used dialyzing fluid as well as a control unit, which permits a mutual filling of the two chambers.
In order to be able to ensure a continuous flow of dialyzing fluid through the dialyzing fluid chamber of the dialyzer, two balancing chamber are connected in parallel in practice, said balancing chambers supplying the dialyzer alternately with fresh dialyzing fluid. A balancing unit with two balancing chambers is known for example from DE 28 38 414.
During a dialysis treatment, the dialyzing fluid flow typically amounts to 500 ml/min, but can amount to up to 1000 ml/min depending on the given treatment situation. In the case of a dialysis period of 4 hours, this means a dialyzing fluid requirement which typically amounts to between 120 L, but depending on the given treatment situation can also be over 200 L.
On account of the large fluid requirement in dialysis, the preparation of the dialysate from concentrates and pure water (RO water) in the machine has become established, in order to avoid the storage of fairly large quantities of solutions. The RO water is made available centrally in the clinic and distributed via lines to the dialysis machines in the dialysis stations.
In the treatment of an acute renal insufficiency, such as can occur for example after accidents, which calls for intensive-care support for the patient, a RO water connection is generally not present. The dialyzing fluid is then made available to the machine by means of containers, for example canisters or bags.
In order to keep the handling costs down, an attempt is made, especially in the case of intensive-care support for acute renal insufficiency, to reduce the requirement for dialyzing fluid. This is achieved by the fact that the dialyzing fluid is recirculated via the dialyzer for a certain length of time. The dialysate requirement can thus be reduced to values which lie below 100 ml/min.
A blood treatment apparatus with a recirculation circuit is known for example from U.S. Pat. No. 5,685,988. The recirculation of dialyzing fluid should however only be used for the determination of blood treatment parameters.
The problem underlying the present invention is to provide a device for conveying fluids into the treatment unit of a medical treatment apparatus, in particular into the dialyzer of a dialysis apparatus, with which device the requirement for dialyzing fluid can be reduced. A further problem of the present invention is to provide a method for conveying fluids into the blood treatment unit of a medical treatment apparatus, said method permitting a reduction in the requirement for dialyzing fluid. The problem of the present invention is also to provide an extracorporeal blood treatment apparatus with such a device for conveying fluids.
The device according to the present invention and the method according to the present invention are based on the fact that the fluid with which the treatment unit is supplied circulates in a fluid circuit which includes the treatment unit. In order to balance fresh and used fluid which is fed to the treatment unit or carried away from the treatment unit, use is made of a balancing unit which in principle can comprise one or two balancing chambers.
The device according to the present invention and the method according to the present invention are characterised in that the balancing chamber of the balancing unit, or the two balancing chambers of the balancing unit, can be incorporated into the fluid circuit including the treatment unit. It is thus possible to supply fresh fluid continuously to the fluid circuit and to discharge used fluid continuously from the fluid circuit. The supply and discharge of fresh and used fluid can take place at a flow rate different from the flow rate at which the fluid circulates via the treatment unit in the fluid circuit. Consequently, there becomes established in the fluid circuit a “fluid” which, depending on the ratio of the flow rates, lies in concentration between a “fresh fluid” and a “used fluid”. Independently of the supply and discharge of fresh or used fluid, fluid (ultrafiltrate) can also be removed from the fluid circuit including the blood treatment unit, in particular the dialyzer.
In a preferred embodiment of the present invention, the flow rate at which the fluid circulates via the treatment unit in the fluid circuit is greater than the flow rate at which fluid is fed to and discharged from the fluid circuit.
The device according to the present invention comprises a bypass, which connects the discharge line leading from the balancing chamber to the treatment unit to the supply line leading from the treatment unit to the balancing chamber. The bypass permits not only a continuous supply of fresh fluid into the fluid circuit including the treatment unit, but also the maintenance of a fluid flow through the blood treatment unit when the balancing chamber of the balancing unit is being filled with fresh fluid, thereby displacing used fluid. If a balancing chamber with two alternately operating balancing chambers is used, this advantage is admittedly not brought to bear. A particularly preferred embodiment of the present invention thus provides a balancing unit with only one balancing chamber. In this particularly preferred embodiment, the bypass ensures that the fluid flow through the blood treatment unit is not interrupted during the switch-over of the balancing chambers. A simplified design of the balancing unit thus results.
The means for conveying fluid into or out of the balancing chamber and the means for interrupting the supply of fluid into the balancing chamber or the discharge of fluid out of the balancing chamber can be designed differently. The known occluding pumps, into which hose lines can be inserted, are preferably used for conveying fluid. For the interruption of the supply or discharge of fluid, use is preferably made of the known electromagnetically or pneumatically operated shut-off elements, which are disposed in the lines. A control unit controls the means for conveying fluid and the means for interrupting the supply or discharge of fluid. Since occluding pumps pinch off the hose line in the standstill state, the occluding pumps can also replace shut-off elements.
In a particularly preferred embodiment, the means for conveying fluid comprises a first pump, which is disposed in the supply line leading from the fluid source to the balancing chamber. Moreover, the conveying means comprises two further pumps, which are disposed in the discharge line leading from the balancing chamber to the blood treatment unit. Of these two pumps, one is disposed in the section of this discharge line which leads to the point at which one connection of the bypass is connected to the discharge line, whilst the other pump is disposed in the section of this discharge line which leads away from the connection point of the bypass. The flow rates of these two pumps in the discharge line determine the flow rate at which fresh fluid is fed to the fluid circuit and used fluid is carried away from the fluid circuit.
In a particularly preferred embodiment, the means for interrupting the supply and/or discharge of fluid comprise a first shut-off element, which is disposed in the first supply line leading from the fluid source to the balancing chamber, a second shut-off element, which is disposed in the second discharge line leading away from the balancing chamber and leading to the drain, a third shut-off element, which is disposed in the second discharge line leading away from the balancing chamber and leading to the blood treatment unit, and a fourth shut-off element, which is disposed in the second supply line leading from the treatment unit to the balancing chamber. All the shut-off elements are controlled by the control unit.
In the particularly preferred embodiment, the control unit is designed such that the first and second shut-off elements are opened and the third and fourth shut-off elements are closed in a first work step of a first work cycle of successive work cycles, the first and third pumps being in operation. In the first work step, the balancing chamber is filled with fresh fluid, used fluid thereby being displaced. During the filling procedure of the balancing chambers, the fluid flow through the treatment unit is not interrupted. The first work step is followed by a second work step, in which the first and second shut-off elements are closed and the third and fourth shut-off elements are opened, the second and third pumps being in operation. In the second work step, the fluid circulates in the fluid circuit including the blood treatment unit. Fresh fluid can also be, but does not have to be, fed to the fluid circuit or carried away from the fluid circuit.
A further preferred embodiment provides for the integration of a further shut-off element in the bypass. This shut-off element serves for the better filling and venting of the system before the treatment is carried out. On the other hand, the circulation in the fluid circuit can also be interrupted with the shut-off element in the bypass.